As a result of cold carbide precipitation, lattice defects, so that the corrosion resistance of straight seam welded pipe decreased. The corrosion resistance of the straight seam welded pipe after solution treatment is restored to the best condition.The solution temperature is determined mainly by the chemical composition. In general, alloying elements, high content of grades, solution temperature should be increased accordingly. Especially manganese, molybdenum, nickel, silicon content of long straight welded pipe, only to improve the solution temperature, to fully dissolve in order to achieve softening effect. However, stabilized steel, such as the Longitudinal Welded Pipe, the solution temperature is high when the stability of the carbide elements fully dissolved in the austenite, in the subsequent cooling will be in the form of Cr23C6 precipitation in the grain boundary, China ppgi corrugated steel sheet causing intergranular corrosion.
In order to stabilize the carbide elements do not break down, not solid solution, generally the lower limit solution temperature. Straight seam steel pipe manufacturing is simple, students to create high yield, low resources, rapid development. Spiral welded pipe strength is generally higher than the Longitudinal Welded Pipe, can be used to create a narrow billet diameter pipe larger pipe, but also with the same width of the raw material to create pipe diameter pipe. However, compared with the same length of the straight seam, the weld length to add 30 to 100%, and students have lower production rate. Therefore, most of the smaller diameter of the welded pipe to accept straight seam welding, large diameter welded pipe is mostly accepted spiral welding. Although the welded steel pipe production line is to create wind-induced security, but there will be some unavoidable small problems occur, so the steel pipe in the factory before doing the testing links will be less, perhaps that is equally important. Straight seam steel pipe welding should be done to complete the mechanical properties test and flattening test and flaring test, and to meet the standards requirements. Pipe should be able to withstand a certain amount of pressure, if necessary, 2.5Mpa pressure test, to maintain a minute without leakage.
It is permissible to replace the hydrostatic test with eddy current testing. Eddy current testing method is to probe fixed in the rack, testing and weld to maintain 3 ~ 5mm distance, by the rapid movement of the weld pipe to conduct a comprehensive scan of the weld, the flaw detection signal by the eddy current detector automatic processing and automatic sorting, To achieve the purpose of testing. Longitudinal Welded Pipe Application: In the country is mainly used in water projects, petrochemical industry, chemical industry, power industry, agricultural irrigation, urban construction. For liquid delivery with: water supply, drainage.
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